Specific interaction of radioactive anti-androgen TSAA-291 with androgen receptor in rat prostates

Study of the effect of an anti-androgen (oxendolone) on experimentally induced canine prostatic hyperplasia. II. Endocrinological analysis

The results of hormonal investigation of effects of an antiandrogen, Oxendolone (OXD), alone or in combination with medroxyprogesterone acetate (MPA), on experimentally induced canine BPH are reported. Seventeen beagle dogs were divided into 5 groups: 2 castrate controls for Group 0, 3 BPH controls for Group 1 which received 3 alpha-androstanediol (3 alpha-A) and estradiol (E2) for one year, and 12 dogs consisting of 3 groups which received 3 alpha-A and E2 for 6 months followed by testosterone propionate (TP) and E2 for another 6 months. The last 3 groups were treated with either 200 mg/week of OXD (Group 3) or OXD + 30 mg/week of MPA (Group 4), and otherwise untreated with these hormones (Group 2, T-E controls). On the blood hormone analysis, both T and 5 alpha-dihydrotestosterone (DHT) were generally lowered in the T-E administered groups (Group 2, 3 and 4) compared to those in Group 1. While MPA significantly decreased these androgen levels, OXD did not influence at all. The concentrations of E2 were similar. Although T content in the prostate did not differ significantly within the experimental groups, DHT was the highest in Group 1 and the lowest in Group 4 and was nearly the same level to Group 0. MPA reduced tissue DHT content but OXD did not. In the receptor assay study, nuclear androgen receptor (AR) content in Group 3 and 4 was significantly lower than that in Group 1. No obvious decrease in nuclear AR content could be seen among the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyproterone acetate prevents translocation of the androgen receptor in the rat prostate

The translocation of the androgen receptor in prostatic tissue has been studied under the influence of different ligands (testosterone, methyltrienolone and cyproterone acetate) in vivo and in vitro. Nuclear and cytoplasmic androgen receptors were estimated using an exchange assay with [3H]methyltrienolone ( [3H]R1881) 1 h and 16 h after injection in castrated rats of either 100 micrograms testosterone (T), 10 mg cyproterone acetate (CA) or the combination of T and CA. Within 1 h after T administration, nuclear receptor levels increased with a concomitant depletion of cytosol receptors. In the CA-treated rats nuclear receptor levels were not different from those of control castrated animals and there was no depletion of cytosol receptors. The combined treatment of T and CA resulted in a partial depletion of cytosol receptors and a simultaneous increase of nuclear receptors. The absence of an increase in nuclear androgen receptors in CA-treated animals cannot be explained by a delay in translocation, because even 16 h after CA injection, only a very small number of nuclear receptors were detectable. Incubation of minced prostatic tissue with [3H]CA or [3H]R 1881 resulted in receptor translocation only in the R1881 incubations and confirmed the in vivo results. Competition studies with different steroids and cytosol receptor (non-activated, 8S form in low salt gradient) or nuclear receptor (activated 3.6S form in high salt gradient) of prostatic tissue show that CA can compete with R1881 for specific androgen-binding sites with a similar relative binding affinity for both receptor preparations. The present results provide evidence that CA prevents translocation of the androgen receptor to the nucleus, although CA can be bound with similar affinities to the nuclear receptor and the cytoplasmic receptor. We propose that the anti-androgenic action of CA involves an inhibition of receptor translocation.